At the last Jini Community Meeting, Tim O'Reilly noted that
Jini and JavaSpaces need a "killer app". Maybe this could be
a candidate: a
JavaSpaces-based MTA. By making all the pieces of MTA
functionality fine-grained and decoupled, you should be able
to build - in theory :-) - a very scalable mailer. Now the
question becomes one of transactions per second...